1. Technical Field of the Invention
This invention relates to a method for controlling bud growth in plants. More particularly, this invention relates to the use of dimethyl 2,3,5,6-tetrachloroterephthalate for controlling the growth of axillary buds in tobacco plants.
2. Description of the Prior Art
Near maturity, the apically dominant terminal bud of the tobacco plant develops into a reproductive bud that eventually produces flowers. These flowers, if allowed to mature, develop into seed heads. As the seed heads mature, lateral buds develop in the leaf axils of the plant. These lateral or axillary buds (suckers) grow as vegetative shoots that eventually develop floral parts for reproduction. During this flowering and reproductive process, most of the plant's energy and nutritional resources are directed to its floral parts, diverting vital resources away from other plant tissues such as the leaves. This adversely affects the leaf tissue, reducing the size, yield and ultimately the quality of the tobacco leaf.
In the practice of tobacco production, the terminal bud is removed at or before the flowering stage; a practice known in the art as topping. Topping facilitates the development of a large tobacco leaf which is commercially desirable. However, removal of the terminal bud destroys apical dominance, resulting in the accelerated growth and development of the axillary buds. The uncontrolled growth and development of these suckers again reduces the nutrient supply available to the leaf tissue, consequently resulting in leaves of inferior quality and size. These suckers must be continuously removed to achieve the desired purpose of topping, i.e., improved size, yield, and leaf quality.
The earliest attempts for controlling sucker growth involved removal of the suckers from the tobacco plant by hand. Since the suckers were not all in the same developmental stage, the field had to be worked several times before complete control could be achieved. These manual methods were time consuming, laborious and expensive. A more efficient and cost effective means for controlling axillary bud growth was therefore needed. Several chemical growth controlling agents have been suggested and are in present day use.
In the practice of controlling axillary bud growth by chemical means, the tobacco plant is first topped to remove the terminal buds. Axillary bud development is then controlled by subsequently spraying the tobacco plant with a chemical growth controlling agent specific for the inhibition of axillary bud growth and development.
Among the most widely used chemical agents for tobacco sucker control is maleic hydrazide. Maleic hydrazide is a systemic type regulator that is readily translocated throughout the tobacco plant. This compound is active in meristematic tissues, i.e., bud tissues, of the plant, functioning as a cell division inhibitor. Both the timing of application and the environmental conditions are important for the maximum effectiveness of this compound. If applied too soon after topping, the compound can adversely affect the leaf expansion of developing tobacco leaves. If applied under low humidity conditions, the uptake of the compound can be severely curtailed. In addition, there have been some recent questions regarding the mammalian toxicology of the compound.
The C.sub.6 -C.sub.12 saturated fatty alcohols have also found use as chemical sucker controlling agents. These compounds are contact type regulators that must directly contact each axillary bud in order to be effective. The fatty alcohols destroy the water retaining membrane of the axillary buds, resulting in complete desiccation of the bud tissue. However, the tobacco grower must pay particular attention when using these compounds, as too great a concentration of active compound can also affect the developing crop leaves.
Recently, the dinitroanilines have been found to be effective tobacco sucker controlling agents as disclosed in U.S. Pat. Nos. 3,880,645; 4,046,809 and 4,123,250. The dinitroanilines are contact-local-systemic agents, inhibiting localized cell divisions in the meristematic tissues. Again, this type of agent must be applied at the correct time, i.e., after the young leaves of the tobacco plant have sufficiently developed, or malformation of the desired crop leaves may subsequently occur, reducing the crop yield and marketability of the leaves.
It would, therefore, be desirable to provide an axillary bud controlling agent that exhibits good efficacy while not causing injury to the developing crop. Accordingly, it is an object of the present invention to provide a chemical method for inhibiting bud growth on plants without adversely affecting the desirable portions thereof.
Another object is to provide a chemical composition which is economical to produce and use, and safe to handle. Other objects and advantages of the present invention will become apparent from the description of the invention which follows.